Download - Basal Ganglia, Cerebellum and Movement
Basal Ganglia, Cerebellum and Movement
CBA 571 Structure of the Human Body(Chapter 10, Lundy-Ekman, emphasis on pp 190-215)
Gib Willett, P.T., M.S., O.C.S., C.S.C.S.Associate Professor, UNMC P.T. Education
Objectives:
Explain the movement related functions of the basal ganglia and cerebellum.
Identify the basal ganglia and cerebellum in diagrams and on models.
Describe the neural pathways between these areas and the cerebrum which influence movement.
Describe most likely symptoms resultant from damage to a given region or pathway presented in this module.
Introduction
B.G. and cerebellum contain large collections of nuclei that modify movement on an ongoing basis
The motor cortex sends information to both areas and both respond back to cortex through the thalamus (gatekeeper to cortex)
Introduction
B.G. motor related signals to the motor cortex are inhibitory
Cerebellar motor related signals to the motor cortex are excitatory
Balance of these systems allows for smooth, coordinated movement
Basal Ganglia
What does ganglia usually refer to? Collection of cell bodies outside the CNS
What are the Basal Ganglia (B.G.)? B.G. are actually a collection of ganglia deep to
the white matter of the cerebral cortex Components of the B.G. include:
Caudate Putamen Globus pallidus Subthalamic nucleus Substantia nigria There are more, but focus will be on the above
five due to their involvement with movement
Lentiform nucleus
Basal Ganglia Location
Basal Ganglia Location
Ventricles Thalamus B.G. component: Caudate nucleus B.G. component: PutamenWhere are the Globus Pallidus,
Subthalamic Nucleus and Substantia Nigra?
Basal Ganglia: Location
Frontal plane section of cerebrum
Basal Ganglia
Sequence movement Regulate muscle tone and force Two basal ganglia pathways influence
movement Promotion of certain movement patterns
(synergies) Inhibition of certain movement patterns
(synergies) Lesions of the basal ganglia result in
disturbances of muscle tone and dyskinesias Hyperkinesia Hypokinesia
Basal Ganglia: Specifics
Caudate & Putamen receive majority of input from cortex (L-E only refers to the putamen) Doorway into basal
ganglia Reciprocally
interconnected with the substantia nigra
Basal Ganglia: Specifics
Substantia nigra Pars compacta
(SNpc)- receives input and sends information back
Produces dopamine which is critical for normal movement
See Parkinson’s Disease in L-E
Pars reticularis (SNpr)- receives input and sends it out to control head and eye movements
Basal Ganglia: Specifics
Globus pallidus Most output from putamen
goes to globus pallidus but not all…….(see figure 10-4, p223 in L-E for a more detailed diagram)
Both interna (not shown in L-E) and externa communicate with the subthalamic nucleus
Interna sends major inhibitory output from B.G. to cortex via thalamus
Interna also has output to midbrain to assist in postural control (see L-E diagram)
Cerebellum
“Little brain” – outer cortex, inner white matter, deep nuclei
Coordinates movement: compares what you wanted to do (cortex), to what happens (proprioceptive feedback), and corrects the movement if needed.
Works ipsilaterally (cerebrum entirely contralateral)
Dorsal viewX-section showing cortex and deep nuclei
Ventral view
Cerebellum
Cerebellum
Summarized by 3’s 3 highways leading in and out “peduncles”
Superior – connects to midbrain Middle – connects to pons Inferior – connects to medulla oblongata
3 lobes – anterior, posterior and flocculonodular
3 broad classes of human movements controlled for by the cerebellum (see L-E)
Equilibrium – vestibulocerebellum Gross limb movements – spinocerebellum Fine distal movements - cerebrocerebellum
Cerebellum
3 input tracts Spinocerebellar -
proprioceptive feedback
Climbing fibers - feedback from ascending tracts via medulla
Pontine fibers - feedback from cerebral cortex
These fibers must cross then enter cerebellum
Cerebellum – “fun facts”
High density of neurons in cerebellar cortex results in cerebellum accounting for 1/10 of total brain volume but contains more than 50% of CNS neurons
Involved in motor learning process Once cerebellum receives intent to move
message, it provides information on movement direction, timing and force
Ballistic movements – too fast for feedback so predictions are made and modified via cerebellum based on experience (circuts change with repetition of an activity)
Cerebellar Lesions
Primarily coordination, proprioception and equilibrium related difficulties
Signs of cerebellar problems are manifested ipsilateral to the side of the lesion
Signs of cerebellar lesions include: Hypotonia – flabby muscles, often pendulous
reflexes Dysmetria – past pointing, missing the mark Dysdiadochokinesis – inability to make rapidly
alternating movements
Cerebellar Lesions
Signs of cerebellar lesions continued: Dysynergia - decomposition of movement
ie. complex movements performed as a series of successive simple movements
Intention tremor – occurs with movement Ataxia – stumbling gait
Alcohol abuse depresses cerebellar circuts (includes dysarthria)
Nystagmus – slow component towards the side of the lesion
Conclusion
Basal Ganglia – basically sequences movement and regulates muscle tone and force
Cerebellum – basically compares actual motor output to the intended movement and adjusts the motor output as necessary to meet movement expectations
Conclusion